Contra Costa, California, United States [County]; population was 803,732 in 1990; housing units was 316,170 in 1990; location is 37°56'N 121°57'W; land area is 720.29 square miles (460,985 acres); water area is 81.89 square miles (52,410 acres); FIPS code is 13 [SourceCBP]